Method and apparatus for treating wells

ABSTRACT

A method of preventing the flow of fluid into a low-pressure zone of earth formation traversed by a well bore when said fluid is placed in the well bore, in which a liner is temporarily employed to block off said low pressure zone. Apparatus for performing such method in which the liner is provided with a bypass valve, opposing packers, and a releasable connection with a running in string of pipe.

"United States Patent Lyle B. Scott.

References Cited UNITED STATES PATENTS Waitz Grant Brown..... Baker et a1. Brown Howard et al.

Primary Examiner.lames A. Leppink Attorneys-Donald W. Banner, William S. McCurry, Lyle S.

Motley and C. G. Stallings ABSTRACT: A method of preventing the flow of fluid into a low-pressure zone of earth formation traversed by a well bore when said fluid is placed in the well bore, in which a liner is temporarily employed to block off said low pressure zone. Apparatus for performing such method in which the liner is provided with a bypass valve, opposing packers, and a releasable connection with a running in string of pipe.

PATENTEU Auclols'n SHEU 1 BF 4 INVENTOR. 0 46 5. 66077 ATTOZA/EV PATENTED AUG! 0 l97| SHEET 3 BF 4 A TTOE/VEV BACKGROUND OF THE INVENTION manently cement the zone off, but yet due to the low-pressure condition in such zone, fluid will flow off into the earth at said zone, thereby making it impossible to perform, for example, such operations as may require reverse circulation as a phase of the operation, wherein fluid will be caused to flow down the casing and upwardly through an inner string of tubing or alternatively downwardly through a string of tubing and then upwardly through the tubing casing annulus.

On the other hand, the presence of such a low pressure zone interferes with the filling of the well bore with fluid whereby to effectively cause the packing off a well packer in the well bore below the low-pressure zone, when it is desired to set such a packer to treat a formation below the packer or straddled by the packer and a bridge plug set below the formation to be treated. An example of the need for reverse circulation in the last-mentioned type of well treatment is the need to circulate sand off of the bridge plug which settles thereon or which is placed thereon in certain operations, whereby the bridge plug will be freed so as to be released from anchored engagement with the well casing.

In any event, the problem involves the fact that the lowpressure formation zone will not support a column of fluid in the well casing, but instead such fluid will flow off into the low-pressure zone, in some instances where the fluid is drilling .mud', contaminating the zone, and in other instances where the fluid may be a treating fluid, causing the undesirable loss of the treating fluid, on the one hand, or the inability to maintain sufficient fluid head above the packer so as to cause the packer to be effectively set and anchored in the well casing, on the other hand. This problem is obviated by the present invention inasmuch as a liner is provided which, during the running of the tools into the well bore on a running in string of pipe, is placed in a position at which it straddles the low-pressure zone and prevents communication between that zone and the well bore, so as to effectively provide an annular space between the liner and the running in string of pipe in which a column of fluid may be supported while'that column of fluid is blocked off from access to the low pressure zone.

, A typical problem to be solved by the method of the present invention exists, for example, in areas where three separate and distinct productive earth zones are traversed by a well bore. and the upper and lower zones are productive and therefore are to be preserved, but these upper and lower zones are relatively low pressure zones; while the intermediate zone is one which requires stimulation, but which, following stimulation, will produce at a comparatively high pressure, requiring that the formation pressure be well contained following the treating operation. Under these circumstances, it will be apparent that not only must the upper and lower zones be isolated from the intermediate zone but also, following completion of the treatment of the intermediate zone, it may be necessary that the well be killed by the placement in the well of a body of weighted fluid which will contain the formation pressure until it is desired that the well be put back on production. Such operations are impossible in the event that the upper zone is in communication with the well bore and is incapable of supporting the hydrostatic column of weighted fluid which will bleed off into the upper zone, reducing the effeetiveness of the weighted fluid and also contaminating the upper zone. In such operations, it will be apparent that the lower zone may be effectively isolated from the intermediate zone by the setting of a retrievable bridge plug in the well casing between the intermediate and lower zones, but, in order to assure retrievability of such a bridge plug, it is necessary in some instances that reverse circulation be employed to wash sand from above the bridge plug so that the same is free for recovery.

DESCRIPTION OF THE PRIOR ART Heretofore in the fluid treatment of wells, such as in the selective fracturing or acidizing of subsurface earth formation zones, various approaches have been taken in an effort to prevent loss of treatment fluids into low pressure sections of the earth, so as to more effectively perform the treating operations by assuring that all of the section of earth has been treated. Soluble solids have been employed, entrained in the treating fluid so as to block the How of fluid into more permeable or lower pressure regions; temporary sealing elements entrained in the fluid, have also been employed for such purposes (see U.S. Letters Patent No. 2,754,910). On the other hand, means have heretofore been provided whereby a liner may be placed at a particular earth zone within the well bore to block the flow of fluid into that zone while another zone is being treated or for other reasons to prevent the loss of fluid into a low-pressure zone (see US. Letters Patent No. 3,067,819).

As distinguished from these prior efforts, however, the present invention contemplates not merely preventing the flow of fluid into a low-pressure zone, as in the case of the soluble solid blocking agents or thetemporary perforation sealing elements, but also the formation of an annular clearance space about the string of drill pipe or tubing through which the treating fluid is being injected into a selected formation, whereby not only is the selected formation effectively treated but also, without regard to the time necessary to complete the operations and without regard to temporarily halting the flow of treating fluid, reverse circulation may be accomplished through a region of the casing which is inherently incapable of supporting a fluid column which would enable such reverse circulation. Moreover, the present invention contemplates the formation of such an annulus about the aforementioned pipe string whereby the annular space may be loaded with fluid above a packer, for example, so as to assure SUMMARY Accordingly, an object of the invention is to provide a method of preventing the flow of fluids from a well bore into a low-pressure zone of the earth formation traversed by the well bore when such fluid is placed in the well bore.

More specifically, an object of the invention is to provide a method of preventing the flow ofi'luid into a low-pressure well zone by placing a liner within the well bore so as to seal off the low-pressure zone from the well bore, whereby an annular space will be provided between the liner and a running in string of pipe, on which the usual tools may be run into the well for the treating of another zone within the well.

Still another object is to provide a liner apparatus useful in the practice of the aforementioned method, such apparatus comprising a body and opposing spaced packers forming a seal, whereby to block off a low-pressure zone in a well bore, and the body further being provided with valve means whereby fluid pressure differential is balanced when the liner is to be retrieved.

Still another object of the invention is to provide such a liner, wherein a releasable connection is provided with the running in string of pipe, whereby the liner may be placed in the well bore at a desired location so as to effectively seal off a low-pressure zone, the liner being run into the well bore on a running in string of pipe having other usual tools mounted therein, and the liner being retrievable by the running in string of pipe following the treatment of the well as desired.

Other objects and advantages of the invention will be hereinafter described or will become apparent to those skilled in the art, and the novel features of the invention will be defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. la and lb are views partly in longitudinal section and partly in elevation showing a well extending through an earth formation, with a liner located at the low-pressure zone and the high-pressure zone being straddled by a packer and a retrievable bridge plug, FIG. 1b being a downward continuation ofFIG. 1a;

FIGS. 2a and 2b are enlarged longitudinal sectional views, showing a liner made in accordance with the invention in a running in condition;

FIG. 3 is a transverse sectional view as taken on the line 33 of FIG. 2b;

FIG. 4 is a transverse sectional view as taken on the line 4-4 of FIG. 2b;

FIG. 5 is a detail view illustrating the connector means for releasably connecting the liner to the running in string of pipe and in a running in condition;

FIG. 6 is a view corresponding to FIG. 5, but showing the connector means in an intermediate condition for closing the liner bypass passage;

FIG. 7 is a view diagrammatically illustrating the manipulative steps for running, closing, releasing, and retrieving the liner;

FIG. 8 is a fragmentary view in longitudinal section and elevation, showing the liner bypass passage closed;

FIG. 9 is a fragmentary view in longitudinal section and elevation, showing the connector means released; and

FIG. 10 is a fragmentary view in longitudinal section and elevation showing the liner bypass passage reopened for retrieval from the well.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. Ia and lb, the present invention involves method steps and apparatus whereby fluid, such as well-treating fluid, such as formation-fracturing fluid, acid, or other fluid, may be placed in a subsurface earth zone A, while such fluid is prevented from entering another earth zone B. In the illustration, the zone B is above the zone A and will herein be referred to as a low-pressure zone in the sense that fluid will enter the low-pressure zone B from the well bore W at a pressure less than is required to cause the entry of fluid into the formation A from the well bore. As is customary in many wells, the well bore has well casing C set therein and defining the effective well wall, the casing having been perforated at P1 at the zone A and at P2 at the zone B. These perforations P1 and P2 may be suitably made as by conventional bullet or jet perforators so as to establish communication between the respective zones A and B and the well bore W. If both zones are productive of well fluids they may be produced through separate conduits, one zone producing through the casing C and the other zone producing through a tubing, not shown, for example.

As an example of the problems solved by the present invention, it may occur that the zone B is a low-pressure but productive zone which should be preserved when it is necessary or desirable to treat the lower zone A which has a formation pressure greater than zone B or has a greater resistance to penetration by treating fluids than zone B. Under these conditions, the zone B must be isolated from the well bore if the zone A is to be treated with fluid. On the other hand, the zone B may be incapable of sustaining in the well bore a column of fluid sufficient to enable treatment of the zone A, since in some operations a packer must be set above zone A and be effectively held anchored by a column of fluid thereabove, and it is impossible to circulate fluid to wash zone A or wash sand from a packer or bridge plug set below zone A.

A specific problem is illustrated in FIGS. la and lb, wherein a bridge plug assembly 1 is set in the casing C below the zone A, and a packer assembly 2 is set in the casing C above the zone A. This bridge plug 1 may be constructed in accordance with the disclosure of U.S. Letters Patent No. 3,332,494, and typically. includes packing cup means 3 carried by a body 4, and adapted to form a seal between the body 4 and the well casing C. Also carried by the body 4 and actuatable in response to fluid pressure acting on the packing cup 3 are anchor slips 5, expansible by a cone 6 when the body tends to move axially relative to friction drag means 7 which prevent movement of the anchor slips 5. The bridge plug also has a running and recovery head 8, whereby the plug may be run into the well and located at the desired position to enable treatment of the zone A and may later be retrieved. In the present illustration, the head 8 is adapted to be engaged by a running and recovery tool 9 carried beneath the packer 2 in a conventional manner, whereby the packer 2 and the bridge plug 1 connected thereto by the tool 9 may be run into the well together on a running in string of pipe or tubing S, the bridge plug being released from the tool 9 when it is in its desired location, and the packer 2 then being elevated in the well bore W to a location above zone A where the packer 2 may be set. This packer is a conventional type, an example of which is disclosed in U.S. Letters Patent No. 3,094,169. In any event, the packer 2 includes a packer rubber 11 adapted to form a seal between the body of the packer 2 and the casing C when the packer is set, the packer also including anchor slips l2 and hold down slips I3, respectively expansible into gripping engagement with the casing C to anchor the packer assembly 2 in position in the casing C. In some instances the packer 2 is held firmly set and anchored by the pressure of fluid in the casing C above the packer 2. In order to relieve this pressure by effecting fluid balancing of the packer 2 when it is to be released, an unloader valve I4 is in the pipe string S above the packer 2, such a valve being disclosed in detail in U.S. Letters Patent No. 3,094,306.

In accordance with the present invention, there is also set in the casing C a retrievable liner assembly L, the purpose of which is to block off the formation B from the well bore while defining with the running in string S an annular space 15 which is a continuation of the annular space 16 between the casing C and the running in string S. The running in string S has a connector member 17 cooperable with means in the liner L, as will be hereinafter more fully described, whereby the liner assembly may be run into the well on the string S and released from the connector I7 when the liner is at the desired location in the casing C. As illustrated in FIG. 1a, the liner is located at a position at which it extends through the region of the casing spanning zone B, the liner having packer cups l8 and 19 in sealing engagement with the casing C at locations straddling the zone B. Valve ports 20 in the liner L are closed during treatment of formation zone A, but, as will be hereinafter more fully described these ports 20 will be opened to balance the pressure across the liner when the liner is to be retrieved.

This liner assembly L will now be more specifically described with reference to FIGS. 20 and 2h. At its upper end, the liner assembly includes a tubular coupling 21 which supports the rubber or other elastomeric packer cup 18, the coupling being threadedly connected as at 22 to a downwardly extended tubular body 23 which is of indefinite length, depending upon the depth of the zone B to be straddled by the liner. At its lower end, the liner body is provided with a tubular valve housing 24 having the above-mentioned valve ports 20 therein, the valve housing being threaded as at 25 or otherwise made a part of or connected to the tubular body 23.

Rcciprocably disposed in the valve housing 24 is a tubular inner body section 26 having an outwardly extended flange 27, the body section 26 being held in assembly with the housthat the liner assembly,

ing 24 by means of a coupling nut 28 threaded on the housing Y24 and having an inturned flange 29 in spaced relation to the lower extremity of the housing 24 so as to limit reciprocation or telescopic movement of the housing 24 and the inner body section 26. This body section 26 extends downwardly from the housing 24 and supports the lower rubber or other elastomeric packing cup 19 previously referred to and a tubular connector body 30 is threaded as at 31 to the body 26 and extends I downwardly therefrom for cooperation with the connector 17 in the running in string S, as will be hereinafter described.

Within the housing 24, the body section 26 is provided with a sealing ring means at 32 sealingly engageable with the inside i open (see FIG. 2b so as to establish communication between the axially extended space outside of the valve housing 24 between the packer cups 18 and 19 and the inside of the body section 26. In other words, when the ports 20 are open, then the pressure across the packing cups is balanced.

The valve sleeve 34 is provided with a seal ring 37 sealingly engaged in the bore 35, and spring means in the form of a coiled spring 38 seating at the top of bore 35 and acting I downwardly on the sleeve 34 normally act to hold the sleeve in a lowermost position at which stops, in the form of radially inwardly extending pins 39 engaging at the upper ends of slots in the valve sleeve 34, limit downward movement of the sleeve 34.

Now it is apparent that the inner body section 26 when in its lowermost position as seen in FIG. 2b, with its flange 27 engaged with flange 29 of nut 28, has its seating surface 33 downwardly displaced from the lower limit of movement of the sleeve 34; but when the inner body 26 is moved upwardly, as seen in FIG. 8, the seating surface 33 will engage the surface 36 of valve sleeve 34 and partially compress spring 38, thereby moving the sleeve 34 upwardly. Thereafter, fluid pressure in bore 35 will provide a force tending to hold the valve 1 means tightly closed.

Means are provided for releasably connecting the connector means 17 in the pipe string S and the connector body 30 of the liner L. In the illustrative embodiment, the body 30 has a bore 40 in which a connector sleeve 41 is retained by a ring 42 welded to or otherwise made a part of the connector body 30.

i v has diametrically outwardly projecting pins adapted to fit in the slots 43 as diagrammed in FIG. 7 and indicated by the ary rows, and as will be more apparent from the following description of the running and recovery of aliner L.

The liner L is shown in the running condition in FIGS. 2a and 2 b, wherein it will be noted that the connector pins 44 are engaged at the lower extremities of slot sections 43a. Thus, as

the string 8 is moved downwardly in the casing C the pins 44 pull downwardly on the connector body 30 and the inner body section 26, the flange 27 of the latter, in turn, pulling downwardly on the valve housing 24 and tubular body 23, so as a whole, will move downwardly, with valve ports 20 open.

When the liner L has been moved downwardly in the casing C to a position at which the packer cups l8 and 19 straddle the zone to be blocked off, say the zone B of FIG. 1, the string S is then simultaneously rotated to the right and lifted, to cause pins 44 to pass through the diagonal slot sections 430 to the top of slot sections 43b, whereupon an upward force will be transmitted from the string S to the connector housing 30 and to the inner body section 26 of the valve means, moving the body section 26 to the position shown in FIG. 8, at which the valve means is closed. Thereafter, the string S is lowered to any desired location, and the liner L will hang in the casing C due to friction of the cups 18 and 19 on the casing. If desired, additional anchor means may be provided to assist in securely holding the liner L in the desired location. In any event, with the liner L so disposed in the casing C, the casing perforations P2 are isolated between the packer rubbers l8 and 19 and the body of the liner, so that no fluid in the casing can pass into the formation B; but the annular space 16 between the liner body and the running in string is unobstructed to permit filling of the casing with fluid or the pumping of fluid into the casing, or circulation of fluid through the casing.

When the pipe string S is being removed from the well, the pins 44 of connector member 17 will enter the slot sections 43, and by manipulation of the string may be caused to traverse slot section 430 into slot section 43a, from which the pins 44 may move upwardly. Such upward movement of the pins 44 will causethem to engage an internal shoulder 45 in the valve sleeve 34 so as to pull the sleeve upwardly, opening the ports 20 to balance pressure across the linerfThereupon the liner assembly may be pulled from the well along with the pipe string S, following completion of a well-treating operation now to be described.

Assuming that the well is as shown in FIGS. la and lb, completed through the upper zone B and the lower zone A, and it is desired to treat zone A, while zone B is blocked off, the steps are as follows.

First the packer assembly 2, with the bridge plug 1 attached thereto by the tool 9, is connected to the lower end of a length of the pipe string S, including, if necessary the unloader valve 14. This length of string is then run into the well in the usual manner. The liner L is then installed in the well below a length of the pipe string having a coupling member 17 therein, so that as the string is run further into the well, the liner will be pulled downwardly. Further lengths of pipe string are added and lowered into the well until the liner L is at its desired location, with the packing cups l8 and 19 straddling the zone B.

Thereupon, the string S is raised slightly and rotated to move the inner valve body 26 to the valve closing position and release the connector means 17 from the liner. Next, the pipe string S will be further lowered, until the bridge plug 1 is at its desired location in the well, below the zone A. At this point, the pipe string will be operated to release the bridge plug 1 from the tool 9, as is customary, and the pipe string S will then be raised until the packer 2 is positionedat the desired location in the well above the zone A. Then the packer 2 may be set, as by manipulating the pipe string.

Now the tools are all located in the well so that treating fluid may be placed in the zone A, as by pumping treating fluid from the earths surface to force the fluid into the zone A. If high pressure is required to so place the treating fluid, the height of the fluid column in the casing C is not sufficient to assure that the packer 2 will hold, the casing annulus may be filled with fluid, such as weighted drilling fluid, to a level above the liner L if necessary, and the zone B will not be contaminated by the drilling or other fluid in the annulus.

After the treating operation is completed, the pipe string S is manipulated to open the unloader valve 14 and release the packer 2, whereupon, the fluids in the well bore may be circulated out, as by pumping a flushing fluid down the string S and out of the casing C, such flushing operation washing away any sand or other sediment that has been purposely placed or settled out on top of the bridge plug 1, as indicated at 50.

Then the pipe string is lowered to effect reengagement of the tool 9 with the head 4 of the bridge plug 1, so that the packer and plug are again joined for removal from the well. Upward movement of the pipe string S then results in engagement of the connector member 17 in the connector sleeve 41; whereupon manipulationof thestring S will allow passage of the connector member through the sleeve 41 and engagement of the pins 44 with the valve sleeve 34, whereby the valve means will be opened to facilitate the removal of the entire string of tools, including the liner L from the well bore.

Opening of the valve means as just described establishes communication between the space defined between the liner body 23 and the casing C and the annular space between the running in string S and the casing C so that differential pressure will not interfere with removal of the liner assembly, the same merely moving upwardly through any fluid in the well casing as such fluid bypasses through the liner body 23, flowing through the valve member 34 about the connector member 17. In order that the connector member 17 may be of sufficient size and strength so as to effectively interconnect adjacent lengths of the pipe string S, it must be of substantial diameter in the illustrative embodiment leaving only a small annular clearance between itself and the valve member 37. Therefore, in the preferred embodiment, connector member 17 is provided with a suitable number of longitudinally extended grooves 17a constituting flow passages enabling large volume flow of fluid as the liner is moved upwardly in the well casing C.

While a bridge plug 1 has been referred to which is run in and retrieved below a packer 2, it will be understood that the plug 1 may be separately run in some instances, say on wire line equipment as is well known. In any event, the invention has application with or without a bridge plug in the well, as for example where only the packer must be set, but an upper low pressure zone prevents circulation back to the surface of the earth or loading of the annulus with weighted fluid to assure proper functioning of the packer 2.

Other changes in the method herein disclosed and in the details of the liner or other tools without departing from the spirit of the invention are defined in the appended claims. For example, if a low pressure zone is below the zone to be treated, the liner L may be turned end for end and run into the well below a packer, such as the packer 2, and placed so as to straddle the lower low-pressure zone during treating of the higher zone above.

lclaim:

l. The method of treating a well having a low-pressure zone spaced from a zone to be treated, including the steps of running into the well a pipe string having a liner releasably carried thereby and also having a packer carried thereby, locating said liner at said low-pressure zone on said pipe string, releasing said liner from said pipe string and straddling said low-pressure zone with said liner, moving said pipe string in said well, setting said packer, treating said well by placing fluid in said zone to be treated, releasing said packer, moving said pipe string and reconnecting said liner to said pipe string, and removing said pipe string and said liner from the well.

2. The method of claim 1, including circulating a flushing fluid into said well and from said well before removing said pipe string and said liner.

3. The method of claim 1 wherein said low-pressure zone is above said zone to be treated, and including the step of loading with fluid the space between said liner and said string of pipe and between said string of pipe and the well wall above said packer, in advance of treating said well.

4. The method of claim 1, wherein said low-pressure zone is above said zone to be treated, and including the step ofloading with fluid the space between said liner and said string of pipe and between said string of pipe and the well wall above said packer, in advance of treating said well, and the step of circulating fluid through said pipe string and to the top of the well after releasing said packer and before removing said pipe string and said liner.

5. The method of claim 1, wherein a bridge plug is releasably carried by said packer, and including the additional steps of moving said pipe string in said well, setting said bridge plug and releasing said bridge plug from said packer before said steps of moving said pipe string in said well and setting said packer. 

1. The method of treating a well having a low-pressure zone spaced from a zone to be treated, including the steps of running into the well a pipe string having a liner releasably carried thereby and also having a packer carried thereby, locating said liner at said low-pressure zone on said pipe string, releasing said liner from said pipe string and straddling said low-pressure zone with said liner, moving said pipe string in said well, setting said packer, treating said well by placing fluid in said zone to be treated, releasing said packer, moving said pipe string and reconnecting said liner to said pipe string, and removing said pipe string and said liner from the well.
 2. The method of claim 1, including circulating a flushing fluid into said well and from said well before removing said pipe string and said liner.
 3. The method of claim 1, wherein said low-pressure zone is above said zone to be treated, and including the step of loading with fluid the space between said liner and said string of pipe and between said string of pipe and the well wall above said packer, in advance of treating said well.
 4. The method of claim 1, wherein said low-pressure zone is above said zone to be treated, and including the step of loading with fluid the space between said liner and said string of pipe and between said string of pipe and the well wall above said packer, in advance of treating said well, and the step of circulating fluid through said pipe string and to the top of the well after releasing said packer and before removing said pipe string and said liner.
 5. The method of claim 1, wherein a bridge plug is releasably carried by said packer, and including the additional steps of moving said pipe string in said well, setting said bridge plug and releasing said bridge plug from said packer before said steps of moving said pipe string in said well and setting said packer. 